Sieve cleaner for a plansifter

ABSTRACT

A sieve frame for a plansifter has a sieve covering, a bottom, and at least one sieve cleaner including a foot and a plurality of cleaning heads. The cleaning heads may have a brush-like or nubby configuration. The cleaning heads are configured to move erratically on the bottom in response to a vibrating movement of the sieve frame. At least a part of the foot closest to the cleaning heads resiliently supports the sieve cleaner such that the cleaning heads are under an elastic intial tension against the sieve covering.

FIELD OF THE INVENTION

The invention relates to a sieve frame for plansifters, the sieve framehaving a sieve covering, a bottom, and a sieve cleaner for the sieveframe. Such sieve cleaners are inserted in the sieve frame of theplansifter so that they will move below the sieve covering in responsethe shaking movement of the sieve and, in doing so, bring their cleaningdevices into contact with the sieve covering in order to clean thelatter.

BACKGROUND OF THE INVENTION

With conventional sieve cleaners, the cleaning devices are notconstantly in contact with the sieve covering, but the cleaning effectis created essentially by the cleaning devices hitting against the sievecovering. This is facilitated, for example, by the fact that the sievecleaner rests with one foot on an ondular grid arranged in parallel tothe sieve cleaner, which is set vibrating as it moves across the ondulargrid.

A conventional sieve frame has a sieve cleaner tiltingly supported withits foot on the bottom of the frame such that, at any given time, only apart of the cleaning brushes engage the sieve covering. Another sievecleaner is known which has the form of a three-armed star whose cleaningdevices are arranged in the area of the free ends of the threecantilever arms arranged in an angular distance of some 120 degrees.This sieve cleaner rests on the level sieve bottom with one foot sothat, with the shaking motion of the sieve, the sieve cleaner executes awobbling movement and hits the sieve covering. The foot can engage in abottom-clearing device that supports the clearing of the sieve-throughstoward a slot opening provided at the edge of the sieve frame.

The advantage of this known sieve cleaner is that it allows a smalloverall height of the sieve frame, and that it can easily reach into thecorners of the sieve frame with its cantilever arms so that the sievecovering is thoroughly cleaned, including in the corner zones.

When the sieve cleaner bumps against the edge of the sieve frame, thefree ends of two arms are in contact with the edge of the sieve framewhile the third arm points to the center of the sieve. This results inthe fact that cleaning devices treat the central area of the sievestatistically more often than the peripheral areas. This can cause anuneven cleaning effect and lead to an increased wear of the sievecovering in the center of the sieve.

The problem to be solved by the invention is to provide a sieve frameand a sieve cleaner that allow an intensive as well as gentle cleaningof the sieve covering.

SUMMARY OF THE INVENTION

This problem is solved by a sieve frame comprising a sieve covering, abottom, and at least one sieve cleaner having a foot and a plurality ofcleaning heads having, for example, a brush-like or nubby configuration.The heads are configured to move erratically on the bottom in responseto a shaking or vibrating movement of the sieve frame. One of the footand at least part of the foot closest to the cleaning heads resilientlysupports the sieve cleaner, for example by a spring, such that thecleaning heads are under a elastic initial tension against the sievecovering. The problem further is solved by a sieve cleaner for use withthe sieve frame, the foot of the sieve cleaner being arranged so as tobe offset with respect to the cleaning heads. The part of the footclosest to the cleaning heads is located between the cleaning heads andthe center of gravity of the sieve cleaner.

Various advantageous embodiments of the invention can be taken from theappended claims.

With the sieve frame in accordance with the invention the cleaningdevices are resiliently prestressed against the sieve covering by a footsupported by a spring so that potential dimensional tolerances in thedistance between the sieve bottom and the sieve covering, e.g. owing toa slight arching of the sieve bottom, do not cause the sieve cleaner toget jammed.

The cleaning effect is not provided by hitting against the sievecovering, but instead by the fact that the cleaning devices are runningover the sieve covering. The fact that all cleaning devices arecontinually and efficiently cleaning the sieve more than compensates forforgoing the hits against the sieve covering. Another advantage resultsfrom more evenly distributed contact of the cleaning devices with thebottom, thus resulting in less wear and tear in one particular area.

According to another aspect of the invention, in an embodiment of thesieve cleaner, the bulk of the cleaning devices is essentially arrangedin a line, and a spacer that is not, or at least less densely, fittedwith cleaning devices protrudes from the line of cleaning devices towardone side.

When the sieve cleaner bumps against the edge of the sieve frame, it canbe aligned in such a manner that the line of cleaning devices is almostin parallel with the edge of the sieve frame. This assists in arelatively large surface of the sieve covering being treated by thecleaning devices in the area close to the edges, while thespacer—protruding to the inside at this moment—is less or not at allinvolved in the cleaning. In this way, on the statistical average, amore even cleaning of the sieve covering is achieved and an excessivewear of the sieve covering in the central area of the sieve is avoided.

Preferably, the spacer is not fitted with cleaning devices and isarranged in a T-shape in reference to the line of cleaning devices. Alsopreferably, the foot on which the sieve cleaner rests on the level sievebottom, which can simultaneously serve as a bottom-clearing-device, isprovided under the spacer so that it is in contact with the sieve bottomin at least two places. This serves the purpose of limiting the possiblemovement of the sieve cleaner so that the entire line of the cleaningdevices is permanently kept in contact with the sieve covering.

The sieve frames of a plansifter usually are of a square layout. It ispossible to obtain a specifically even cleaning effect when the lengthof the sieve cleaner measured from the line of the cleaning devices tothe free end of the spacer has almost half the edge length of the sieveframe.

The preferred embodiments will be explained in detail by means of thefollowing drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Depicted in

FIG. 1 is a of a sieve cleaner, with some features of the inventionshown;

FIG. 2 is a lateral view of the sieve cleaner in accordance with FIG. 1;

FIG. 3 is a view from under the sieve cleaner in accordance with FIGS. 1and 2;

FIG. 4 is the layout of a sieve frame of a plansifter with a sievecleaner, illustrating further features of the invention;

FIG. 5 is a vertical section through the sieve frame in accordance withFIG. 4;

FIG. 6 is a partial section through a sieve cleaner in accordance withan embodiment of the invention;

FIG. 7 is a longitudinal section of a sieve cleaner in accordance withanother embodiment;

FIG. 8 is the top view of a sieve cleaner in accordance with anotherembodiment, and

FIG. 9 is a section along the line IX—IX in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sieve cleaner 10 depicted in FIGS. 1 through 3 comprises arubber-elastic body that has an almost T-shaped layout. This body 12forms two cantilever arms 14 which are essentially aligned on one lineand carry on their upper side several cleaning devices 16 arranged inone line. The cleaning devices 16 can be provided by naps that form onesingle piece with the body and have a nubby configuration, or,alternately, by bunches of bristles inserted in the body 12.

The body 12 also forms a spacer 18, arranged in T-shape with referenceto the line of cleaning devices 16 and placed out-of-line somewhat belowthe cantilever arms 14.

At the underside of the cantilever arms 14 stiffening fins 20 areprovided, which link up with one end of the spacer 18. At the oppositeend, the spacer 18 has a rising projection 22, the upper end of which ispositioned lower than the upper ends of the cleaning devices 16.

One foot of the sieve cleaner is formed by two cams 24, 26 provided atthe underside of the spacer 18. The cam 24 has a circular layout and islocated in the vicinity of the end of the spacer 18 facing the arms 14,while the cam 26 has an oblong layout and protrudes in axial directionbeyond the opposite end of the spacer 18.

While the cantilever arms for the sieve cleaner 10 in accordance withFIGS. 1 through 3 are slightly bent, FIGS. 4 and 5 depict a modifiedembodiment with the arms 14 linked to one another in a straight-linedway and carrying a continuous straight line of cleaning devices 16. Asfor the rest, the sieve cleaner in accordance with FIGS. 4 and 5 has thesame structure as the one in accordance with FIGS. 1 through 3.

Moreover, FIGS. 4 and 5 depict a sieve frame 28 of a plansifter. Saidsieve frame has a level bottom 30 and is delimited by four walls 32, 34.Additionally, the sieve frame 28 has a sieve covering 36 that isarranged at a distance in parallel to the bottom 30. Together with thebottom 30, the wall 34 of the sieve frame forms a slot opening 38 forthe sieve-throughs.

With its cams 24, 26 aligned on a straight line, the sieve cleaner 10rests on the level bottom 30 of the sieve frame, and its height isadapted to the sieve frame so that all cleaning devices 16 come againstthe underside of the sieve covering 36, as is shown in FIG. 5. Becausethe cams 24, 26 and the bottom 30 define one contact line that runs inrectangular direction as compared to the line of cleaning devices 16,the sieve cleaner 10 per se could tilt around this contact line. Thisis, however, prevented by the cleaning devices 16 coming into contactwith the sieve covering. Therefore, the cams 24 with their flatunderside glide over the surface of the bottom 30 and can hence serve asbottom clearing device.

Moreover, the height of the cam 26 is dimensioned in such a way that itcan also enter the slot opening 38, as depicted in FIG. 5.

Because the spacer 18 and, consequently, the cams 24, 26 are arrangedout-of-line vis-à-vis the line of the cleaning devices 16, the sievecleaner can tilt around the cam 24. Normally, however, this is preventedbecause the center of gravity S of the sieve cleaner is placedout-of-line vis-à-vis the cam 24 slightly toward the cam 26. If, inexceptional cases, for example, when strong vibrations occur, the sievecleaner actually tilts, the rotational area will be limited by the factthat the projection 22 leans onto the sieve covering. A tilting of thesieve cleaner 10 can also take place if the distance between the bottom30 and the sieve covering 36 is changed owing to distortion or archingof the bottom 30. In this case, the tiltable support of the sievecleaner prevents any jamming between the bottom and the sieve covering.A certain elastic resilience of the arms 14 can further contribute tothis effect.

FIG. 6 depicts a variant in which the cam 24 rests on the body 12 of thesieve cleaner via a spring 40. This method allows a precise adjustmentof the elastic prestress that presses the cleaning devices 16 againstthe sieve covering 36.

The sieve frame 28 has a roughly square layout with an edge length a.The length L of the sieve cleaner 10, measured from the line of thecleaning devices 16 to the free end of the spacers 18, is roughly a/2.

During operation of the plansifter, the sieve frame 28 is put in ashaking motion, so that the sieve cleaner 10 executes erratic movementson the bottom 30. When the sieve cleaner has almost reached theorientation as depicted in FIG. 4, the cleaning devices 16 can clean theleft half of the sieve covering up to the sieve edge, however, theycannot reach the right half of the sieve covering because the spacer 18will then bump against the wall 34 of the sieve cleaner. When the sievecleaner has reached the opposite orientation, likewise, only the righthalf of the sieve covering can be cleaned. As the length L of the sievecleaner is almost half the edge length of the sieve frame, there willneither be a large gap nor a major overlap between the two areas of thesieve covering that can be cleaned during the different orientations.The same applies analogously for orientations of the sieve cleaner whichare rotated by 90 degree as compared to the orientation depicted in FIG.4. Because orientations of the sieve cleaner vary statistically, analmost even cleaning and, consequently an almost even wear of the sievecovering, is achieved on average for the entire surface of the sievecovering. Owing to the statistic nature of this consideration, it is notimportant to be very exact in dimensioning the length L.

FIG. 7 depicts another embodiment of a sieve cleaner 10, which isstructured similarly to the sieve cleaner in accordance with FIG. 6.However, the spring 40 that supports the cam 24 is not provided as ahelical spring, but as a long stretched-out leaf spring positioned in asimilarly oblong recess 42 on the underside of the body 12.

FIGS. 8 and 9 depict a sieve cleaner 10 whose body 12 is designed likethose of conventional sieve cleaners as a flat plate that has a layoutin the form of an equilateral triangle with rounded convex sides and isfitted with cleaning devices 16 on the entire circumferential edge. Onthe underside of the body 12, a cylindrical bushing 44 is formed in thecenter and holds and allows vertical movement of a piston that forms thefoot 46 of the sieve cleaner. The spring 40 sitting between the foot 46and the body 12 is again provided as a helical spring and held in thebushing 44.

The sieve cleaner in accordance with FIGS. 8 and 9 also rests with itsfoot 46 on the level sieve bottom so that the cleaning devices 16 aresoftly pressed against the sieve covering by the spring 40.Consequently, all the cleaning devices 15 are constantly in effect. Whenthe sieve bottom is slightly distorted, the spring 40 can give wayelastically so that the sieve cleaner will not get jammed in theclearance between the sieve bottom and the sieve covering.

Just as the body 12, the foot 46 can be made of a rubber-elasticmaterial. When the sieve cleaner moves inside the sieve frame, it ispossible that the foot 46 “grinds” on the level sieve bottom so that aminor vibration is created, which will support the cleaning effect.

What is claimed is:
 1. A sieve cleaner for a sieve frame for flatsifters comprising a sieve covering and a bottom, the sieve cleanercomprising: a foot and a plurality of cleaning heads, said heads beingconfigured to move erratically on the bottom of the sieve frame inresponse to a vibrating movement of the sieve frame, wherein at leastone of the foot and at least a part of the foot closest to the cleaningheads, resiliently supports the sieve cleaner such that the cleaningheads are under an elastic initial tension against the sieve covering,wherein the foot of the sieve cleaner is arranged so as to be offsetwith respect to the cleaning heads, and the part of the foot closest tothe cleaning heads is located between these cleaning heads and thecenter of gravity of the sieve cleaner, wherein a majority of thecleaning heads are arranged essentially in one row, and a spacer havingone of no cleaning heads and fewer cleaning heads than are in said onerow, projects to one side away from the row of cleaning heads, andwherein the spacer forms a foot which is offset on the whole withrespect to the row of cleaning heads and defines at least two supportpoints which are arranged at a distance from one another on a straightline perpendicular to the row of cleaning heads.
 2. The sieve cleaner ofclaim 1, further comprising arms for carrying cleaning heads, whereinthe sieve cleaner is made of elastically flexible material at least inthe area of the arms carrying the cleaning heads.
 3. The sieve cleanerof claim 1, further comprising arms for carrying the row of the cleaningheads, wherein the spacer is arranged in a T shape with respect to thearms of the sieve cleaner carrying the row of the cleaning heads.
 4. Thesieve cleaner of claim 1, wherein the spacer has a projection on thefree end, the projection having a height that is lower than the heightof the cleaning heads.
 5. The sieve cleaner of claim 1, wherein thecleaning heads have one of a brush-like and nubby configuration.
 6. Thesieve cleaner of claim 1, wherein one of the foot and at least a part ofthe foot closest to the cleaning heads resiliently supports the sievecleaner via a spring.
 7. A sieve system comprising: a sieve frame forflat sifters having a sieve covering and a bottom; and a sieve cleanerfor the sieve frame, said sieve cleaner having a foot and brush-like ornubby cleaning heads arranged in essentially one row and configured tomove erratically on the bottom in response to a vibrating movement ofthe sieve frame, wherein at least one of the foot and a part of the footclosest to the cleaning heads supports the sieve cleaner over a springso that the cleaning heads are under a flexible initial tension againstthe sieve covering, and a spacer with one of no cleaning heads and fewercleaning heads than are arranged in said one row projecting to one sideaway from the row of cleaning heads, wherein the length of the sievecleaner measured from the row of cleaning heads to the free end of thespacer is approximately half the edge length of the sieve frame, thesieve frame being approximately square, and wherein the spacer forms afoot which is offset on the whole with respect to the row of cleaningheads and defines at least two support points which are arranged at adistance from each other on a straight line perpendicular to the row ofcleaning heads.
 8. The sieve system of claim 7, wherein the sievecleaner is supported on a smooth bottom of the sieve frame.
 9. The sievesystem of claim 7, further comprising arms for carrying the row ofcleaning heads, wherein the spacer of the sieve cleaner is arranged in aT shape with respect to the arms of the sieve cleaner carrying the rowof the cleaning heads.
 10. The sieve system of claim 7, wherein thespacer has a projection on the free end, the projection having a heightthat is lower than the height of the cleaning heads.